<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>vue计数器
    </title>
</head>

<body>
    <div class="app">
        <div class="input-num">
            <button @click="add">+</button>
            <span>{{ num }}</span>
            <button @click="sum">-</button>
        </div>


    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        var app = new Vue({
            el: ".app",
            data: {
                num: 1
            },
            methods: {
                add: function () {
                    if (this.num < 10) {
                        this.num++
                    } else{alert('别点了')}

                },
                sum: function () {
                    if (this.num > 0) {
                        this.num--
                    } else{alert("也不要点了")}
                }
            }
        })
    </script>
</body>

</html>